Not applicable.
The present invention relates to an image sensing apparatus. In particular, the present invention relates to an image sensing apparatus and to a microcontroller for an image sensing apparatus.
Recently, digital printing technology has been proposed as a suitable replacement for traditional camera and photographic film techniques. The traditional film and photographic techniques rely upon a film roll having a number of pre-formatted negatives which are drawn past a lensing system and onto which is imaged a negative of a image taken by the lensing system. Upon the completion of a film roll, the film is rewound into its container and forwarded to a processing shop for processing and development of the negatives so as to produce a corresponding positive set of photos.
Unfortunately, such a system has a number of significant drawbacks. Firstly, the chemicals utilized are obviously very sensitive to light and any light impinging upon the film roll will lead to exposure of the film. They are therefore required to operate in a light sensitive environment where the light imaging is totally controlled. This results in onerous engineering requirements leading to increased expense. Further, film processing techniques require the utilizing of a xe2x80x9cnegativexe2x80x9d and its subsequent processing onto a xe2x80x9cpositivexe2x80x9d film paper through the utilization of processing chemicals and complex silver halide processing etc. This is generally unduly cumbersome, complex and expensive. Further, such a system through its popularity has lead to the standardization on certain size film formats and generally minimal flexibility is possible with the aforementioned techniques.
Recently, all digital cameras have been introduced. These camera devices normally utilize a charge coupled device (CCD) or other form of photosensor connected to a processing chip which in turn is connected to and controls a media storage device which can take the form of a detachable magnetic card. In this type of device, the image is captured by the CCD and stored on the magnetic storage device. At some later time, the image or images that have been captured are down loaded to a computer device and printed out for viewing. The digital camera has the disadvantage that access to images is non-immediate and the further post processing step of loading onto a computer system is required, the further post processing often being a hindrance to ready and expedient use.
At present, hardware for image processing demands processors that are capable of multi-media and high resolution processing. In this field, VLIW microprocessor chips have found favor rather than the Reduced Instruction Set Computer (RISC) chip or the Complex Instruction Set Computer (CISC) chip.
By way of background, a CISC processor chip can have an instruction set of well over 80 instructions, many of them very powerful and very specialized for specific control tasks. It is common for the instructions to all behave differently. For example, some might only operate on certain address spaces or registers, and others might only recognize certain addressing modes. This does result in a chip that is relatively slow, but that has powerful instructions. The advantages of the CISC architecture are that many of the instructions are macro-like, allowing the programmer to use one instruction in place of many simpler instructions. The problem of the slow speed has rendered these chips undesirable for image processing. Further, because of the macro-like instructions, it often occurs that the processor is not used to its full capacity.
The industry trend for general-purpose microprocessor design is for RISC designs. By implementing fewer instructions, the chip designed is able to dedicate some of the precious silicon real-estate for performance enhancing features. The benefits of RISC design simplicity are a smaller chip, smaller pin count, and relatively low power consumption.
Modern microprocessors are complex chip structures that utilize task scheduling and other devices to achieve rapid processing of complex instructions. For example, microprocessors for pre-Pentium type computers use RISC microprocessors together with pipelined superscalar architecture. On the other hand, microprocessors for Pentium and newer computers use CISC microprocessors together with pipelined superscalar architecture. These are expensive and complicated chips as a result of the many different tasks they are called upon to perform.
In application-specific electronic devices such as cameras, it is simply unnecessary and costly to incorporate such chips into these devices. However, image manipulation demands substantial processor performance. For this reason, Very Long Instruction Word processors have been found to be most suitable for the task. One of the reasons for this is that they can be tuned to suit image processing functions. This can result in an operational speed that is substantially higher than that of a desktop computer.
As is known, RISC architecture takes advantage of temporal parallelism by using pipelining and is limited to this approach. VLIW architectures can take advantage of spatial parallelism as well as temporal parallelism by using multiple functional units to execute several operations concurrently.
VLIW processors have multiple functional units connected through a globally shared register file. A central controller is provided that issues a long instruction word every cycle. Each instruction consists of multiple independent parallel operations. Further, each operation requires a statically known number of cycles to complete.
Instructions in VLIW architecture are very long and may contain hundreds of bits. Each instruction contains a number of operations that are executed in parallel. A compiler schedules operations in VLIW instructions. VLIW processes rely on advanced compilation techniques such as percolation scheduling that expose instruction level parallelism beyond the limits of basic blocks. In other words, the compiler breaks code defining the instructions into fragments and does complex scheduling. The architecture of the VLIW processor is completely exposed to the compiler so that the compiler has full knowledge of operation latencies and resource constraints of the processor implementation.
The advantages of the VLIW processor have led it to become a popular choice for image processing devices.
In FIG. 1A of the drawings, there is shown a prior art image processing device 1a that incorporates a VLIW microprocessor 2a. The microprocessor 1a includes a bus interface 3a. 
The device 1a includes a CCD (charge coupled device) image sensor 4a. The device 1a includes a CCD interface 5a so that the CCD can be connected to the bus interface 2a, via a bus 6a. As is known, such CCD""s are analog devices. It follows that the CCD interface 5a includes an analog/digital converter (ADC) 7a. A suitable memory 35a and other devices 36a are also connected to the bus 2a in a conventional fashion.
In FIG. 1B of the drawings, there is shown another example of a prior art image processing device. With reference to FIG. 1A, like reference numerals refer to like parts, unless otherwise specified.
In this example, the image sensor is in the form of a CMOS image sensor 8a. Typically, the CMOS image sensor 8a is in the form of an active pixel sensor. This form of sensor has become popular lately, since it is a digital device and can be manufactured using standard integrated circuit fabrication techniques.
The CMOS image sensor 8a includes a bus interface 9a that permits the image sensor 8a to be connected to the bus interface 2a via the bus 6a. 
VLIW processors are generally, however, not yet the standard for digital video cameras. A schematic diagram indicating the main components of a digital video camera 10a is shown in FIG. 1C.
The camera 10a includes an MPEG encoder 11a that is connected to a microcontroller 12a. The MPEG encoder 11a and the microcontroller 12a both communicate with an ASIC (application specific integrated circuit) 13a that, in turn, controls a digital tape drive 14a. A CCD 15a is connected to the MPEG encoder 11a, via an ADC 16a and an image processor 17a. A suitable memory 18a is connected to the MPEG encoder 11a. 
In order for an image sensor device, be it a CCD or a CMOS Active Pixel Sensor (APS), to communicate with a VLIW processor, it is necessary for signals generated by an image sensor to be converted into a form which is readable by the VLIW processor. Further, control signals generated by the VLIW processor must be converted into a form that is suitable for reading by the image sensor.
In the case of a CCD device, this is done with a bus interface in combination with a CCD interface that includes an ADC. In the case of an APS, this is done with a bus interface that also receives signals from other devices controlled by the VLIW processor.
At present, an image sensing interface does not form part of a VLIW processor. This results in the necessity for an interface to be provided with the image sensor device or as an intermediate component. As a result, a bus interface of the VLIW processor is required to receive signals from this suitable interface and from other components such as memory devices. Image processing operations result in the transfer of large amounts of data. Furthermore, it is necessary to carry out a substantial amount of data processing as a result of the size of the instruction words used by the VLIW processor. This can result in an excessive demand being made of the bus interface. Further, as can be seen in the description of the prior art, it is necessary to provide at least two interfaces between the image sensor and the VLIW processor.
Applicant has filed a large number of patent applications in the field of integrated circuits and integrated circuit manufacture. As a result, the Applicant has spent much time investigating commercially viable integrated circuit devices that would be suitable for mass manufacture. As a result of the time and effort spent by the Applicant in developing this technology the Applicant has investigated the possibility of using microcontrollers to achieve low cost, yet complex image processing devices.
A microcontroller is an integrated chip that includes, on one chip, all or most of the components needed for a controller. A microcontroller is what is known as a xe2x80x9csystem on a chip.xe2x80x9d A microcontroller can typically include the following components:
CPU (central processing unit);
RAM (Random Access Memory);
EPROM/PROM/ROM (Erasable Programmable Read Only Memory);
bus interface/s;
timers; and an
interrupt controller.
An advantage of microcontrollers is that by only including the features specific to the task (control), cost is relatively low. A typical microcontroller has bit manipulation instructions, easy and direct access to I/O (input/output) data, and quick and efficient interrupt processing. Microcontrollers are a xe2x80x9cone-chip solutionxe2x80x9d which reduces parts count and design costs. The fact that a microcontroller is in the form of a single chip allows the manufacture of controlling devices to take place in a single integrated circuit fabrication process.
In this invention, the Applicant has conceived a microcontroller that includes a VLIW processor. In particular, the Applicant believes that a microcontroller can be provided that is specifically suited for image processing. It is submitted that this approach is generally counter-intuitive, since VLIW processors are generally used in the format shown in the drawings indicating the prior art. The reason for this is that the fabrication techniques are extremely complex. However, Applicant believes that, in the event that a sufficiently large number of microcontrollers are manufactured, the cost per unit will drop exponentially. Applicant intends utilizing the microcontroller of the present invention in a device that it is envisaged will have a high turnover. At present, it has been simply more convenient for manufacturers of image processing devices to obtain a standard VLIW processor and to program it to suit the particular application.
According to a first aspect of the invention, there is provided an image sensing and processing apparatus that comprises
an image sensor that is capable of generating signals carrying data relating to an image sensed by the image sensor; and
a microcontroller that comprises
a wafer substrate;
VLIW processor circuitry that is positioned on the wafer substrate;
image sensor interface circuitry that is positioned on the wafer substrate and is connected between the
VLIW processor circuitry and the image sensor, the image sensor interface circuitry being configured to facilitate communication between the VLIW processor circuitry and the image sensor; and
bus interface circuitry that is discrete from the image sensor interface circuitry and is connected to the
VLIW processor circuitry so that the VLIW processor circuitry can communicate with devices other than the image sensor via a bus.
According to a second aspect of the invention, there is provided a microcontroller for an image sensing and processing apparatus, the microcontroller comprising
a wafer substrate;
VLIW processor circuitry that is positioned on the wafer substrate;
image sensor interface circuitry that is positioned on the wafer substrate and is connected between the VLIW processor circuitry and the image sensor, the image sensor interface circuitry being configured to facilitate communication between the VLIW processor circuitry and the image sensor; and
bus interface circuitry that is discrete from the image sensor interface circuitry and is connected to the VLIW processor circuitry so that the VLIW processor circuitry can communicate with devices other than the image sensor via a bus.
The invention is now described, by way of example, with reference to the accompanying drawings. The specific nature of the following description should not be construed as limiting in any way the broad nature of this summary.